1. Field of the Invention
The present invention relates to an inductor element, and to an integrated electronic component including an inductor element as a part.
2. Description of the Related Art
A RF (radio frequency) system or a RF circuit employed in a mobile phone or the like generally includes an integrated passive device (hereinafter, IPD) as a high-frequency module device, for upgrading the performance and reducing the dimensions and weight. In the IPD, passive components such as an inductor, a capacitor, a resistor, and a filter required according to the design are integrated, among which the inductor rarely fails to be incorporated. The inductor generally has a relatively low Q value, for example in comparison with the capacitor, and hence incorporating the inductor in the IPD often degrades the Q value thereof as a whole. Accordingly, various studies are being pursued for achieving a higher Q value of the IPD that includes the inductor. The techniques related to the IPD can be found, for example, in JP-A-H04-61264 and U.S. Pat. No. 5,370,766, as well as in the non-patent documents 1 and 2 cited here below.
Patent document 1: JP-A-H04-61264
Patent document 2: U.S. Pat. No. 5,370,766
Non-patent document 1: Albert Sutono et al., “IEEE TRANSACTION ON ADVANCED PACKAGING”, VOL. 22, NO. 3, AUGUST 1999, p. 326-331
Non-patent document 2: Guo Lihui et al., “IEEE ELECTRON DEVICE LETTERS” VOL. 23, NO. 8, AUGUST 2002, p. 470-472
For example, the non-patent document 1 describes an IPD manufactured through a low-temperature co-fired ceramic (hereinafter, LTCC) process. In the IPD manufactured through the LTCC process, a plurality of passive components is integrally built in a multilayer ceramic substrate. To form the inductor, a plurality of spiral coils is often stacked in multiple layers in the multilayer ceramic substrate, so as to increase the inductance. The higher inductance generally leads to the higher Q value of the inductor, and hence such structure is advantageous for increasing the Q value of the overall IPD including the inductor.
The inductor thus formed incurs, however, significant parasitic capacitance, because a ceramic material (dielectric material) is interposed between mutually adjacent portions of the coil lead of the spiral coil constituting the inductor, in the IPD manufactured through the LTCC process (spiral coil bears a capacitor electrode pair-like structure formed of the mutually adjacent portions of the coil lead). Besides, in the case where the inductor is constituted of a plurality of spiral coils stacked in multiple layers (multilayer inductor) in the multilayer ceramic substrate in the IPD manufactured through the LTCC process, the inductor incurs significant parasitic capacitance because of the presence of the ceramic material (dielectric material) between the mutually adjacent portions of the coil lead. Naturally, the large parasitic capacitance of the inductor is disadvantageous for increasing the Q value thereof.
In the IPD manufactured through the LTCC process, the inductor, which is a primary constituent thereof, thus incurs significant parasitic capacitance, thereby often inhibiting the increase in Q value of the inductor, and hence in Q value of the IPD as a whole.